1. Field of the Invention
The present invention relates to a monolayer type photoconductor and an image forming device. In particular, the invention relates to a monolayer type photoconductor superior in sensitivity characteristics that allows reliable production while allowing easier confirmation of the sensitivity characteristics, and an image forming device using the same.
2. Description of the Related Art
Generally, an increasing number of organic photoreceptors have been used recently as electrophotographic photoconductors for electrophotographic devices such as a copying machine and a laser printer, because of the requirements for lower price, lower environmental pollution and others. Phthalocyanine pigments, which are sensitive to light at an infrared to near-infrared wavelength region that is irradiated, for example, from a semiconductor laser or infrared LED, have been used widely as charge generating agents for use in such organic photoreceptors.
The phthalocyanine pigments are grouped into non-metal phthalocyanine compounds, copper phthalocyanine compounds, titanyl phthalocyanine compounds, and others, depending on chemical structure, and it is known that each phthalocyanine compound can have various crystal forms based on the difference in its production condition.
Among the various phthalocyanine compound crystals different in crystal form currently available, electrophotographic photoconductors employing titanyl phthalocyanine in the Y-type crystal structure as the charge generating agent are known to have electrical properties more favorable than those employing titanyl phthalocyanine in another crystal form.
The Y-type titanyl phthalocyanine crystal is, for example, a titanyl phthalocyanine crystal having a maximum diffraction peak at a Cu—Kα Bragg angle 2θ of 27.3°±0.2° in the X-ray diffraction spectrum, and disclosed is a method of producing a titanyl phthalocyanine crystal in reaction of a phthalocyanine ring-forming organic compound and a titanium in a dialkylaminoalcohol containing added urea or ammonia at 130° C. for about 4 hours (see, e.g., Patent Document 1).
Also disclosed are methods of preparing a titanyl phthalocyanine crystal in direct reaction between o-phthalonitrile and titanium tetrabutoxide in the absence of a urea compound under the condition at 215° C. for about 2 hours (see, e.g., Patent Documents 2 and 3).
More specifically, disclosed is a method of producing a titanyl phthalocyanine crystal having peaks in predetermined ranges of the CuKα X-ray diffraction spectrum and having no temperature variation peak in the range of 50 to 400° C. in differential scanning calorimetry.
[Patent Document 1] JP-8-176456A (Examples)
[Patent Document 2] JP-3463032B (Claims)
[Patent Document 3] JP-2004-145284A (Claims)
However, although it is possible to prepare titanyl phthalocyanine crystals respectively having a desired crystal form according to the methods in Patent Documents 1 to 3, electrophotographic photoconductors prepared by using the titanyl phthalocyanine crystals obtained often show a significant difference in sensitivity characteristics.
The difference in sensitivity characteristics seems to be caused by fluctuation in dispersibility of the titanyl phthalocyanine crystal in a photo sensitive layer, which is in turn caused by a slight difference in the amount of impurities remaining in the crystal.
Thus, it is needed to measure the sensitivity characteristics actually for control of the fluctuation in quality, which is the reason of the low productivity of the electrophotographic photoconductor.